Variable-frequency radio signaling apparatus



Sept. 19, 1950 E. P. FAIRBAIRN ET AL VARIABLE-FREQUENCY RADIO SIGNALING APPARATUS Filed May 10, 1947 4 Sheets-Sheet l KPEdBmq 822ml? UT $2 $9.228 e: E8. ban

Rub-4E M ESQ! INVENTORS ERIc PLAYF'AHZ FAI RBAI RN ALEXANDER ALBERT CHUBB A TTOENEV Sept. 19, 1950 E. P. FAIRBAIRN ET AL 2,523,105

VARIABLE-FREQUENCY RADIO SIGNALING APPARATUS Filed May 10, 1947 Y 4 Shee ts-Sheet 2 925m]: Q IGmz/s "'finc/t fcFZI'GZ save/s lllll lllllllll lllllllfi lfilplr qfizsmd 7 ,15 42 FILTER 4'4 3 mxen mnumxsn -2:

men 5 5 i lg J8 2 REFERENCE MASTER OSCILLATOR I OSCILLATOR i MASTER oscuuron INVENTORS ERIC PLAYFAHZ FAIRBAIQN ALEgf xwofifi ALBERT CHUBB ATTOQNEY p 1950 E. P. FAIRBAIRN ET AL 2,523,106

VARIABLE-FREQUENCY RADIO SIGNALING APPARATUS Filed May 10, 1947 4 Sheets-Sheet 3 CLUTCHES (-4? 7 5 9 4 9 as 3 IO L INVENTORS 2121c PLAYFAHZ FAIEBAIEN ALE I 3MDEQ ALBERT CHUBB ATTORNEY Sept. 19, 1950 E. P. FAIRBAIRN ET AL VARIABLE-FREQUENCY RADIO SIGNALING APPARATUS 4 Sheets-Sheet 4 Filed May 10, 1947 INVENTORS 5121c PLAYFAHZ F'AJRBAIRN ALEXANDER ALBERT CHUBB ATTQENEY .U 'TE nf-ISTA 'Patented Sept. 19, 1950 maidens- REQUENCY RAnio SIGNALiNG APPARATIIS l Eric Playfair Fairbairnand Alexander Albert.

'Chubb; Coventry, England, assignors to The General Electric England Company, Limited, London,

7 Application May 1 0,1947 ,saarm lmas In -Great Britain October, 31, 1945 Section LPublic Law 690, August s, 1946 Patent expires October. 31,1965 I frequency being a reference frequency i (also usually crystal controlled) or else theraster being composed of the frequency in modulated by the harmonics of the frequency'h (both being usually crystal controlled) and the said other frequency being the variable frequency f. The coincidences referred to occur when beats betweenone of the rasterfrequencies andthe said other frequency lie within a suitable narrow frequency band which may be selected by a suitablefilter.

"If the number of settings ofthe tuning element from'which selection can be made is large, it may be'inconvenient to count all the coincidences up to the desired setting, even if the counting be automatic. It is, therefore, usually desirable to provide means for generating two rasters, one composed of a series of major harmonics and the other of a series of minor harmonics, the former series including for example only every fifth minor harmonic. For instance if it be desiredto count to the setting32 from zero, 6 major harmonics (excluding zerm might be first counted to give a setting of 3O, and two minor harmonics then I counted to reach '32.

The means for generating the beating'oscillations,as well as the amplifying means whereby the oscillations can bebrought to a suitable amplitu de for operating a counter or. indicator; comprisethermionic valves. consequentlywhen' apparatus of the type-set forth is first switched on, some little time passes, whilst the cathodes of the valves areheating 'up, beforethe beating oscillations are being generated and amplified-effectively. It is clearly important to ensure that tuning, whether by an electric motor or by hand, is not started until the said oscillations are being effectively generated as otherwise the counting For instance a. relay controlling the .7 Claims. (01. 250-36) cathode circuit of one of the valves the relay operating when the current therein reaches a predetermined value. However, it is diflicult to ensure thatthe particular valve selected is the one requiring the longesttime for-heating its cathode and the relay may operate before certain of the valves are fully operative. If a thermal relay is provided to introduce delay, it is necessary in order to cover contingencies to adjust it to give a delay time which is considerably in excess of the smallest delay time necessary. Moreover such relays are apt to be unreliable under vibration.

One object of the present invention is to provide apparatus of the type set forth in which the commencement of a tuning operation is delayed until said beating oscillations are being generated and have reached a predetermined amplitude, that is to say until all valves in the apparatus are fully operative. a

Another object of the present invention is'to provide apparatus of the type set forth in which a tuning operation is permitted to take place substantially immediately after all valves in the apparatus are fully operative and said beating oscillations are being produced and have reached a predetermined amplitude.

A further object of the invention is to provide apparatus of the type set forth in which a test for the presence at or above a predetermined amplitude of said beating oscillations is made every time a tuning process is initiated.

A brief description of one form of apparatus of the type set for for the purpose of assisting in the understanding of the present invention,

and a description of two embodiments of the present invention and certain modifications thereof,

, of apparatus of the type to which the present in;

vention relates, v 1 ig. 2a is a diagram illustrating a raster of harmonics relative to a reference frequency,

Figl'2b is a diagramsimilar to Fig. 2a,- but showingfa raster in a differentposition with respect to' said reference frequency,

vFig. 3 shows an alternative arrangement of part ofFig-.1, i i Fig. 4 is a circuit diagram of a beat-counting and condenser-driving circuit which includes one embodiment of-the present invention.

Fig. 5: isa' circuit diagram of a second embodiment of the invention and- OFFICE. a";

is ablock schematic diagram of one form Figs. 6, 7, and 8 illustrate alternative arrangements of parts of the circuits shown in Fig 4. Throughout Figs. 1 to 8 like parts have been given like "references, and all relays and their associatedcontacts areslio'wn conventionally. The

same conventions are also applied to a uniselector voperating coil SM and contacts or banks or conwould have three contacts. The relay contacts are designated by the same capitalletter as that given to the relay and a figure. Thus, in the same example, the three contacts of the 'relay A/fl would be denoted by Al, A2 and A3. 7

Referring to Fig. 1, atunable oscillator I is the :master oscillator'of apparatus requiredto be tuned; to a desired frequency Tuning of the oscillator It is carried out by rotation of a condenser shaft; II ;to a desired position by means about to be described.

,;The output of the oscillator l0, which is of the frequency above referred-to as f, is fed to a mixer circuit 12 where it is modulated by the harmonics ofgaj harmonic generator [3 of, which-more details will'be "given later. Thus there are present in the output of the mixer l2, equallyspaced sidebands of'ithe oscillation supplied by the oscillator 10.

These sidebands of f are passed through a filter amplifier circuit [4 to a second mixer circuit l-5to whichis also fed a reference oscillation, of frequency'a-bove referred to as f0, generated by acrystal controlled oscillator l6.

-.R;eferring now to'Fig.-2 (a), I0 is shown tohave a value'of 2-1; 625 mc./s. and j a valueof 25 mc;/s.. The fundamental frequency oftherharmonic generator-"1'3 (Fig.1) ;is shown as being 450 kc./s.'

andtho'selower'sidebands of which are employed :commenceat 21.4 mc./s., that is the eighth'sideband, and proceed at intervals of 450 kc;/s 'down to '9.25 'mc./s. The "reason for" suppressing the first seven sidebands is that-it is desirable that the amplitudes of the sidebands usedshould be -substantially equal and hence thefirst'seven which have especially largeamplitude are-suppressed by means-of a-suitable filter not :shown. This state ,of affairs, as shown in Fig. 2 (a) will'be named the rest state of the circuit, that is the state existing when the apparatus is first switched onajnd before 'a-tuning operation'is commenced.

the condensershaft II (-Fig. 1 is rotated fromth'e rest position (by means to be described later) the' frequency f is increased and'the raster of harmonics, thefisidebands of 7; also moves 'up the frequency scale. In doing this each sideband filter T1 totwo filters I18 afndglii. Thuswhen any sidebandof 1 comes within 60' kc. /s." of the refer- 'e'ri'ce frequency fc, a beat oscillation "is passed throu h t filter I], to. the-filters l8 and 19. l- Ience', referring to FigQZQasfis increased from 25 mc./s. to 29195 mc./s., elevengsuch :beatoscillationsarepassed to :the; filters, 18" and V I 9.

, denser driving circuit 22.

4 quencies from 22-50 kc./s. and the filter [9 a band of frequencies from 0-23 kc./s.

On passing through the filters l8 and I9 the beats are rectified by 'two, rectifiers 20 and 2! whcs'e outputs are fed to'a beat counting and con- The function of this circuit. 22 is to count the beat oscillations supo'f'harmonics. 'One raster is composed of a series of major harmonics and is shown in Fig. 2. In

this case the fundamental frequency is 450 kc./s. as already stated. The second raster is com- "posed of a series of minor harmonics having a fundamental frequency of kc./s.

The operation using the 90 kc./s. raster is the same as has been described for the 450 kc./s. raster. The way in which the counting of the major and minor harmonics is arranged to operate the shaft l I will "be described later.

Referring in detail to the circuit of the harmonic-ge nerator -l3, pow"er for the generator [3 is supplied by a power unit 23 which is connected to 'two supply-terminals 24 and 25 through a switch 26. Although Fig. 1 shows the power unit 23 supplying power to the generator 13 only, it may, and usually will, supply.power to the remainder of the apparatus. The frequency of oscillation of an oscillation valve 21 is determined byZ-the setting of two relay contacts MI and M2. In the position shown the frequency is arranged to 'be 45( kc./s., and when the switches MI and M2 are in their alternative positions it is arranged to be 90 ire/s. The output from'the valve 2} is fed through afrel'ay contact M3 to one of two multi-vibrators '28 and 2 9. The relay cont acts Mt, M2 and M3 'a-re factu'ated simultaneously by a relay to be described-later and hence when the va1ve 2'| -is oscillating at 450kc./s. the relay contact M3 is in the position shown and the 450 kcj/sjo scillation is fed' to the multi-vibrator 29. LWlintlie relay contacts Ml,-M2 and M3 are switched to their alternative positions the 90 l{c./s.'oscillation is genera-ted and fed to the multivibrator 28. The'multi-vibrators n and2'9 serve togener'atea large number of harmonics from the oscillationssupplied to them.

'If is desirdto rotatethe condenser shaft to a position corresponding to a count of, say, 17 niinc'ir,or"90 'kc./s., stepsffr'om the rest state shown in mg. 2 (a), -the relay contactsMl, M2 aIndjMta're 'set 'to tlie'450 kc./s.position for a admit of "two, making a total -count equivalent to seventeen ninety kc./ s. steps.

In the foregoing description-the output of the harmonic"fgen'erator I3$"was u sed to modulate f theiaster of "mechanic produced as sidebands of j movedf in step "withj and produced beat s -or coincidences, witha reference frequency f0. 3 These beats may be produce d-by modulating f withthe harmonics-generated-by the generator l3 'and 'then -mixing the resulting stationary raster; with ,f.

Fig. 3 showsthe rearrangement of 'Fig.- 1 necessary-to-eifect thisalternative method of producing'ithe beats. "In-Figs. 1'ai1d '3'lik'e'p'arts have been given like references, and it iwillbe se'en that the reference"oscillationof frequency 70 produced bysthe" oscillator Hi is--modulated by the output of the harmonic generatoriii.

The filter i8 is arranged to ipassla" band offrets --:':'The resulting-stationaryraster is -mixed'with f in'the mixer and the beats produced when f. is varied are used as alread described with ref-' erence to Figs. 1 and 2.

Referring to Fig. 4 and the description with:

reference-to Figs. 1, 2 and3, on switching on the apparatus (which may be effected by the switch-4 26 Fig. 1) a relay M (Fig. 4) is operated by current flowing from a positive terminal33 through the coil of the relay M-and a relay contact D2 to earth. The relay contacts Ml, M2 and (Fig. l)there'fore, move to the alternative posi-" tions' to those shown and the apparatus is set to generatea 90 kc./s.raster. t a

When the valve 21, multi-vibrator 28 and oscillator II) are functioning adequately the 90 kc.'/s. raster is produced. I

The sideband frequency of this raster nearest relay CF, this indicating that the oscillator, valve 21, multi-vibrator 28 and at least one of the rectifiers and 2| are working and-that the beat "ing oscillations have reached a predetermined amplitude suiiicient to operate the relay CF. Only after this has been tested can the apparatusoperate. I t

' The relay contact. CFI moves to its operated position and a delay relay D is energised bycurrent flowing from the terminal 33 throughtD;

S is energised and is locked in this position by a relay contact SI which places an earth on the relay S from D2 through a cam switch COR and B. The cam switch COR is operated by a cam are of the make-and-break type such as are commonly used on electric buzzers or tremblers. The'action of the contacts SM! produces current pulses which cause the uniselector arm 34 to be moved rapidly around the contactsro'n SMI until the earthed contact SMI/5 thereon is reached. Current then flows from the terminal 33 through the coil of SM, through theicontacts S02, one coil of a relay SC, contact 8M4, and the arm 34 to earth. SC is thus operated; SC2 disconnects SM from the contacts SM! and connects SM through S5 and a relay contactSAl. toCFi. a v

Whilst this is happening relay contacts SCI and S2 complete the circuit of an electrically,

' operated master clutch MA which then couples relay contacts DI, CFI and SA3 to earth. The; Y

connects the output of the filter 18 from the relay.

CF and hence the apparatus is set to commence a tuning operation about to be described. As

raster to be produced. The relay contact D3 dis- I box 36 with a second gear box 31.

the minor harmonics are now switched err and contacts D3 are open, relay CF releases before counting commences.

QA and QB are major and minor harmonic setting switches respectively, and as in the previously.

quoted example, if a count of 32 minor harmonicsi is required, QA is set to contact 6 and QB is set}.

tocontact 2 as shown. To avoid confusion of; these contact numbers with references they;

thereof. The contacts of this switch are indicated by the consecutive numbers I to 2|.

The arm 34 of SMI isconnected throughits spindle-35 to a cam'switch SM4 which is-op+ erated by a cam 42 on' 'the vspindle35 and is closed only when the arm 34 is on anyofcon The relay ,cOntactD Z putsan earth through two cam switchesCON and SM5 to one side of a "select switch B. The camswitch CON is op erated by a cam 4| on the condenser'sh-aft ram is closed only when the'circuit isinth'e rest'v state. SM5 is operated from a cam 43 on the spindle 3-5 of the uniselector SMfand is closed only when the arm 34'is on contact SMI/ I." r

On closing the select switch B current flows from the terminal 33 through the operating coil of a relay S, switch B, the cam switches SMS and CON and relay contact D2" to earth. Hence relay made from earth on $3 through a relay contact.

SM2 and the coil RP to the terminal 33 and the relay RPdsenergised; The relay contact SM2 is cam operated from a cam 44 on the spindle 35 and opens only when the arm 34 on SMI is on contacts II to 2lthereon. At the moment under consideration SMI is set to contact SMl/E and SM2 is therefore closed. Contacts RP2 connect the output of the rectifier 20 (Fig. 1) to the relay CF, and relay contact RP3 causes an electrically operated fast clutch FA to link the gear The fast{ clutch FA, when engaged, causes the condenser shaft II to' be driven at relatively high speed by connecting the motor Z to the shaft l I through suitable gears in the gear boxes 36 and 31.

As the frequency f is increased by rotation of the shaft l l, successive 'sidebands of f pass through the reference frequency f0 and each coin-- cidence in turn produces a beat oscillation which is rectified by the rectifiers 20 and 2| and causes CF to be operated. Successive operations of CF cause the uniselector' SMI to be moved step --by step until contact H on SMI is reached. After the'contact H has been reached the relay contacts SM2 and'CFl are both open and relay RP is de-e'nergised. The relay contacts RP3 causes the fast" clutch FA to be disengaged and a medium" clutch ME. to be engaged. Engagement of this clutch ME causes the speed of shaft II to be reduc'ed.- The relay contact RP2 opens and the rectified output of the filter I9 (Fig, 1) only is connected to CF. A switch SM3, which is operated by the cam 45 on the spindle 35 and is arranged to close only when the arm 34 is on contacts SMI/II to SMI/2|, closes, and the switch SM4, which is also arranged to operate from the cam 42 o n the spindle 35 and only when the arm 34 is on contacts SMI/H to SMI/2|,operates; the relay'M is energised and the kc./s. raster is produced. CF is then operated each time f is increased by 9'0 kc./s. and the arm 34 on SMI is advanced step by step until contact SMI/121s reached. The circuit for a relay SA is then made from the e'arthed contact SMI/l2 through 5M4 v and S63. SA operates and a relaycontact SM,

disconnects the uniselector coil SM from ;C-1F l A relay contact SAZ operates causingthefimediumf; clutchME to be disengaged and causing a slow clutch SL to be engaged. Operation of the relaycontact SA3 causes the earth to be removed from the moving contact of CF! and to be connected. to the junction of CFI and RV! as shown. QFI, however, remains in the operated position there;- by maintaining an earth on the motor Z which continues to run but the shaft H is rotated at slow'speed. Contacts sA l connect the rectified output of the filter I8 (Fig. 1) to a relay RV.

,fis increased slowly and the motor Z continues torun until the frequency of the nextbeat oscillation comes Within the overlapbetween the. two filters l8 and I9, when both relays RV and CFLoperate. Both brushes-of the motor Zare connected, by contacts CPI, and 'RVI, to earth and the motor stops. V

The apparatus is then tuned to the required frequency. I I

- Fromthe foregoing. description it will be seen that if the switches QA and QB have beenset to required positions and the select switch B isYnot made when the apparatus has warmed up after first switching on, the operation of the delay relay-D, which occurs immediatelyv the valves cone.

apparatus and when the oscillators for producing to Qfikc/sxraster are- Working, CF operates and the relay. S-operates at once "if the select switch B is closed, or,"rif' B is not closed, then S operates as son as B is closed, and'the apparatus is... tuned substantially as. previously described. The effects of the slight differences-between thetwdfigures will be understood by-thoseskilled i i-the art. If the select switch B is then opened S is de-energised and the circuit returns t'o'the rest'state. Hence with thisarrangement a ;test for the pres-ence'of beat oscillations is. made ever time a tuning process is initiated instead of only when-the apparatus is'firstrswitched on, and a tuningprocess is initiated or permitted QnlY-WhEn-Such test indicates that'beat-s a-re pres ent. a Y .l'nstead of the-operation of therelaygcontacts SCi and S2 causing the master clutch MA tobe operated, they may be arrangedto switch on ;th .e motor Z as shown in Fig. 6. 1;,

Furthermore the shaft 4 I may bedriven,nian-u all in which case the master clutch MA may be connectedas shown in Fig. '7 thereby-preventing an operator from turnin the shaft H until beat tt will be seen that the present invention proj-g vides means which ensure that tuning does not commence until the valves generating all the oscillations which combine and produce the 90 kc./s. raster and associated beats are in proper operation and moreover that the delay introduced is substantially as small as possible.

. We claim:-

1.'Multichannel radio signalling apparatus.

. said first oscillation and said plurality of oscillations 'to produce beating oscillations, andmeans for applying said beating oscillations to said responsive means only.

'2. Multi-channel radio signallin apparatus comprising .means for generating a first oscillation, .means for generating a plurality of oscillations of "equally-spaced frequencies, tuning means for varying the relative values of the frequencies of said first oscillation and said plurality of oscil-. lations, control means for operating said tuning means, a clutch device which when operative couples said control means to said tuning means and when inoperative permits relative movement of said. control means and said tuning means, means for beating together said first oscillation and said plurality of oscillations to produce beating oscillations, and means for-applying said beating oscillations to said clutch device to render said clutch device operative only when said beating oscillations exceed a predetermined amplitude. a I

. v3. Multi-channel radio signalling apparatusas claimed in claim 2, wherein said clutch device comprises an electromagnetically operated clutch, a current source for operating said clutch, and a relay for controlling the supply of current from said source to said clutch, the operating winding of. said relay being fed with said beating oscillations and being actuated to render said clutch operative when the amplitude of said beating oscillations exceed said predetermined amplitude. .4. 'Multi-channel radio signalling apparatus comprising means for generating a firstoscillation, means for generating a plurality of oscillations of equally-spaced frequencies, tuning means for varying the relative values'of the frequencies of said first oscillation and said plurality of oscillations, control means for operating said tuning means, a. fixed element,'fixed relatively to said tuning means, a stop device comprising a mov able element-Which, whensaid device is inoperative,,can engage said fixed element to preventoperation of tuning means by said controlmeans, means responsive to oscillations applied thereto exceeding a predetermined amplitude to displace said moving element out of engagement with said fixed element to permit said tuning'element to be operated, -means for beating togethersaid first oscillation and said plurality of oscillation to produce ,beating oscillations, and means for applying-said beating oscillations to said respon sive means. Y I p 5. Multi-c'hannel radio signalling. apparatus comprising means for generating a first oscillai a eee f ccep a l r l 9 r lle.

tions of equally-spaced frequencies, tuning means for varying the relative values of the frequencies of said first oscillation and said plurality of oscillations, an electric motor for operating said tuning means, a current source for operating said motor, a relay device Whichwhen operative connects said source to said motor, means for beating together said first oscillation and said plurality of oscillations to produce beating oscillations, and means for applying said beating oscillations to an operating winding of said relay device to render said relay device operative only when said beating oscillations exceed a predetermined amplitude.

6; Multi-channel radio signalling apparatus comprising. means for generating a first oscillation, means for generating a plurality of oscillations of equally-spaced frequencies, tuning means for varying the relative values of the frequencies of said first oscillation and said plurality of oscillations, driving means for operating said tuning means, switch means which when actuated initiate the operation of said tuning means by said driving means, protective means for preventing the operation of said tuning means by 25 said driving means, even when said switch means are actuated, but responsive to oscillations applied thereto exceeding a predetermined amplitude to permit said operation, means for beating together said first oscillation and said plurality of oscillations to produce beating oscillations, and

means for applying said beating oscillations to said protective means.

7. Multi-channel radio-signalling apparatus according to claim 6, wherein said protective means comprise a first relay having said beating oscillations applied to the winding thereof, and a second relay having its winding in circuit with said switch means and contacts of said first relay and adapted to be actuated upon actuation of said first relay when said switch means are actuated, said second relay being connected to control the operation of said tuning means by said driving means.

ERIC PLAYFAIR FAIRBAIRN. ALEXANDER ALBERT CHUBB.

REFERENCES CITED UNITED STATES PATENTS Name Date Andrews Dec. 15, 1942 Number 

